Why did Ramsay Bolton set Winterfell on fire

Escape from Winterfell

That's how it would end.
At the foot of the walls of Winterfell, in a high snowdrift that she could only guess at in this weather.
Sansa inhaled the icy air and snowflakes stuck her nose together. She couldn't see the ground through the heavy snowfall and darkness.
On the one hand, that was bad, because she could only hope that the snow would pile up high enough to soften her fall enough to save her fate or death.
That was good, on the other hand, because it meant the guards couldn't see her if she got up and headed for the forest.
There was only blackness at her feet. She took one last breath, closed her eyes, and jumped.

***

Sansa had sat in her barren room and tried to concentrate on some embroidery that she had only started to kill time. There had been nothing else for her to do in Winterfell. Outside she would probably have run into Ramsey or one of his playmates, which Sansa had wanted to avoid if at all possible. They were like the dogs she seemed to love so much and would sniff out the slightest excitement in her.

What choice did she have? "There always has to be a Stark on Winterfell." Her father's words still resonated in her heart.
But she knew what had been done to the blonde girl. A few days earlier it had been chased through the woods by Ramsey and Myranda, the kennel master's daughter, and their dogs. The girl had been the game. Sansa hadn't been able to tell exactly what had happened there as she watched the goings-on from the castle walls, but they had only brought the young woman's skin back and the dogs had been covered in blood.
It was no coincidence that the Bolton's coat of arms featured a skinned man, and Ramsey went out of his way to live up to the banner.
She had known what kind of life awaited her at his side. And he would only keep her alive as long as he needed her to father a rightful heir to Winterfell by his name.
After that, Myranda herself would be chased through the woods, teeth bared and lips dripping, while Ramsey enjoyed the spectacle.

They had already locked her up because she was forbidden to leave the castle.
It was thanks to Petyr Baelish's presence alone that she had at least been allowed to move freely within the walls. Even that little freedom would have been taken from her after Littlefinger's departure, who had been called to King's Landing, the Seven might know why.
Ramsey had already indicated that he thought it would be appropriate if his bride could prepare for the wedding and the following night without the distraction, which meant nothing more than that he intended to lock her in her room.
It had to happen that night and she hoped that her helper had not betrayed her and would be waiting for her.

Two days ago the old woman, who was helping her with the most essential chores as a valet, whispered a message to her abruptly. “The wolf forest waits in the night. The North remembers: "None of them dared to speak more.
Those short sentences were all Sansa needed. They meant he was ready and waiting for her.
The wolf forest was behind the north gate and that was usually not very well guarded. Nevertheless, she had realized that she would not be able to leave the castle this way. When they discussed their plan, none of them had thought of it.
Apparently he was relying on her to find a way out because she had known the castle since childhood.

Not far from the north gate stood the ramshackle tower from which her brother had once been pushed. She had intended to pretend that she would go to the crypt if she encountered anyone, but would then have climbed up instead of down. A narrow passage there led to the defensive wall. There she knew a spot near the gate where the wind used to pile up the snow to form a slope, and which hopefully was suitable for jumping down.
If she succeeded, she would only have to walk the long meters to the forest as fast as she could. Once she got to the trees she would be safe. At least if they didn't bring the dogs and if he actually waited for them.
He was to take her away, to White Habour and then across the sea to the legendary "Mother of Dragons" who had become legendary in her lifetime. She was Sansa's only hope of regaining the north and driving the Boltons from their homes instead ill-treated by Ramsey in various ways, and finally being chased to death by his dogs, and Winterfell and the Stark name would be lost for good, and with him the North.

She had let the last hours of the day go by, full of restlessness; her embroidery had looked more like something Arya might have made, not any of her other fine work.
It was shortly before the new moon, which is why you could hardly see a hand's breadth. For hours it had seemed like the snowfall was picking up and the castle had been quiet.
She had hoped that her supposed future husband would use the nights before his marriage to have fun with Myranda.

Believing that she was timing correctly, she quickly put on the warmest clothes she could find. Beyond that, she had had nothing to take with her, because she owned nothing. She had given the pitiful remains of her jewelry to her accomplice as payment and to cover the cost of the trip.

Sansa had opened her door carefully, very slowly to avoid a creak. Then she had stuck her head through the crack and peered up and down the hall. Luckily for her, the corridor had been abandoned in the semi-darkness.
As if it were in no way unusual for the Lady von Winterfell to be walking through the castle shortly after midnight in full traveling clothes, she had straightened her shoulders and set off.
In fact, she had reached the tower without any problems and, as far as she could tell, without being seen. Her heart beat fast in her throat.
She had climbed the broken wooden stairs, wedged her way through the narrow passage, and scurried along the wall to where she had planned to jump down.

***

Because of the heavy snowfall, nothing could be seen. The forest was quiet, somewhere back there in the depths of the night. It was cold. Cold and wet and dark. She had forced herself to open her eyes after a brief moment of drowsiness, but it made little difference. She saw nothing. She remained motionless for a moment, listening for footsteps. Nothing, everything remained calm.

Sansa struggled out of the snow as quietly as she could until she felt firmer ground under her boots again. The thick wool of her clothing pulled her down and she tangled in her cloak when she almost managed to get up. Ice crystals melted on the back of her neck and water ran down her collar. She shivered. But she gritted her teeth and finally it was done. She stood free in front of the high wall of Winterfell, which was now her only point of reference.
From here she ran, into the snowstorm and the blackness, in the direction in which she suspected the forest - and him.
Although she grew up in the north, she had never been able to enjoy riding or even hiking through the snow. While Arya and her brothers roamed through the woods, or drove their horses full of exuberance through the snow around Winterfels, Sansa had preferred to sit in the warm and read songs of knights and beautiful maidens. Or she had sewn and embroidered clothes which, at a young age, she considered worthy of a lady-in-waiting.
Now she cursed herself for it, because she had completely lost her orientation and did not know how to regain it. She had no choice but to keep walking, hoping to get where she wanted to go.
Her breathing sounded loud in her ears and more than once she thought she heard the sniffing and sniffing of the dogs behind her.
But when she turned there was nothing but silence and blackness.

Suddenly she hit something hard. She couldn't prevent a small cry of surprise from escaping from her lips, but at the same time she realized that it was a narrow trunk that had so abruptly stopped her escape.
The first tree of the wolf forest. Everything was still quiet behind her.
She walked slowly now and carefully felt her way on.
Sansa had no idea where to turn, or where exactly he was waiting.
The snow didn't fall so thickly here, but the darkness was impenetrable.
Suddenly an arm wrapped around her shoulders from behind and a gloved hand pressed over her mouth. At that moment the crooked words that followed were the most beautiful sound she could imagine: “Shh, little bird. It's me.".